4 books in series

National Geographic Readers: Level 3

National Geographic Readers: Level 3 is a 4-book series with 4 released primary works first released in 2013 with contributions by Melissa Stewart, Elizabeth Carney, Kitson Jazynka, Libby Romero, and Laura Marsh.

Great Migrations: Whales
National Geographic Readers: What Is an Archaeologist?
Robots
Mars
Sacagawea